The traditional bow, also called a long bow, is typically a solid or laminated wood structure having a variable cross section which is larger in the handle region and which transitions to a generally flat cross section in the limb area, away from the central region.
A more contemporary bow, called a recurve bow, is shaped such that the tips of the limbs of the bow curve away from the archer. This allows for improved spring back and higher arrow velocities. A still more contemporary bow, called a compound bow, has a wheel and pulley mechanism, which further enhances arrow velocity.
The bow originated as a single piece structure made of a single piece of wood. The bow structure was later designed with laminated wood to take advantage of combining different species of wood as well as using strengthening adhesives to bond the plies together. While the laminated structure can resist repeated flexing and is very durable, some disadvantages exist. A laminated structure is limited to a flat geometry, which is an inefficient design when the bow limb is traveling through the air. When the bow is fully loaded and the bow limbs are undergoing maximum deflection, the faster they are able to return, the higher arrow velocity. In addition, the flat panel shaped of a laminated structure has very poor torsional properties. This can decrease the accuracy of the bow system.
Further improvements were made by adding fiber reinforced composites to the wood laminated bow structure. Fibers such as fiberglass, aramid, and carbon fiber have been used in a variety of polymer matrices.
The bow was further advanced by separating the central region (the riser) from the two outer regions (the limbs). The combination of a rigid riser with flexible limbs created a more powerful and accurate bow.
The performance of an archery bow, measured in terms of accuracy, arrow velocity, and numerous other factors, can be affected by a number of characteristics of the bow, such as weight, bending flex, resiliency, vibration damping, and strength.
Arrow velocity is heavily dependent upon the resiliency of a bow, which is a measure of the ability of the bow to recover from a flexed state when the arrow is drawn back. The stiffness of the bow limbs is also important. The stiffness and stiffness distribution along the length of the limb can affect the pull back force required as well as the velocity of the shot.
The accuracy of a bow is another important characteristic. Accuracy is determined by numerous factors. The limbs of the bow must deflect and return on a consistent basis, and the central portion of the bow, the riser, must be sufficiently rigid to not deflect or twist during aiming or shooting. Vibration damping is another critical performance factor. As the arrow is released, vibrations can be generated which can affect the trajectory of the arrow as it exits the bow.
The weight of the bow limbs and the riser is also important. A lighter bow limb can return faster, resulting in a faster shot. A light weight riser provides for an overall lighter bow weight or allows for more weight to be added to the bow system to improve the stability and balance of the bow.
Lastly, the sound the bow makes while shooting is also important when the bow is use for hunting. A more silent bow reduces the chance that the prey will hear the shot and become startled and run away.
Numerous improvements in bow technology and construction have been patented. An example of a laminated structure is shown in U.S. Pat. No. 2,945,488 (Cravotta, et. al). Examples of changing the cross section of the bow limbs to enhance performance are shown in U.S. Pat. Nos. 4,122,821 (Mamo), 6,105,564 (Suppan) and 6,718,962 (Adcock). Examples of modifying the bow limb by adding grooves and slots for the string are shown in U.S. Pat. Nos. 2,836,165 (Bear), 2,957,470 (Barna) and 5,609,146 (Izuta). An example of a bow with tubular limbs in shown in U.S. Pat. No. 4,338,909 (Plummer).
There are also numerous examples of bow limbs having holes, primarily for the purpose of weight reduction of the limbs. Examples are U.S. Pat. Nos. 4,201,183 (Bodkin), 5,150,699 (Boissevain), 5,503,135 (Bunk), 6,698,413 (Ecklund) and 6,067,974 (Islas). In each of these examples, the holes are formed by removing material from the bow structure post fabrication, which weakens the structure and causes instability.
U.S. Published Patent Application US2004/0084039 A1 discloses a bow with a pair of limbs spaced a distance apart either side of the riser. Each bow limb is comprised of a braided fiber reinforced polymer. Apertures are formed at each end of the limb as a means of attaching the limbs to the riser and the wheel mechanism. There is no connection between the limbs which will result in an unstable performance because each limb can operate independently. U.S. Pat. Nos. 4,644,929 (Peck) and 6,964,271 (Andrews) also describe bow limbs formed of a pair of parallel limb elements.
There also exist numerous examples of improvements to the handle riser of the bow system to reduce the weight. These include holes and openings which are formed in the riser to reduce the weight, and constructing the riser from lightweight metals such as aluminum and magnesium. U.S. Pat. No. 5,335,645 (Simonds, et. al) describes an aluminum riser with recesses machined in the structure to reduce the weight. Examples in the market are the Martin Pro Series or Gold Series of compound bows, or the Samick Masters Series of recurve bows. Other examples are shown in U.S. Pat. Nos. 6,257,220 (McPherson, et. al) and 7,066,165 (Perry).
Examples of bow limbs fabricated of fiber reinforced composites are shown in U.S. Pat. Nos. 5,392,756 and 5,501,208 (Simmonds) and 5,657,739 (Smith). Composite materials have also been used to make the bow riser lighter or for improved vibration damping. Examples include U.S. Pat. Nos. 4,693,230 (Sugouchi), 5,269,284 (Pujos, et. al), 5,845,388 and 6,669,802 (Andrews, et. al), and U.S. Published Patent Application No. US2005/0229912 A1 (Piopel, et. al).